A long code is used for channel encryption in a forward channel and to determine the location of a power control bit. The long code also serves to identify terminals operating in a reverse channel and to reduce interference with the signals transmitted by other terminals. The generation of a general long code is illustrated in FIG. 1.
Referring to FIG. 1, a long code 13 is generated from a long code generator 12 according to a long code mask 11 and generally has a length of 42 bits. Then, a mobulo-2 inner product operation 15 is performed using a transmission signal (X) 14 and the long code (Y) 13.
Methods of performing a broadcast/multicast service in the CDMA2000 system require the allocation of a public long code mask using specific identifiers (ID information) as a reference for PLCM allocation, and the ID information may be taken from the respective subscribers or the broadcast/multicast service itself. It is more efficient to use the broadcast/multicast service as the reference, whereby one public long code mask is allocated to each group of subscribers using the broadcast/multicast service, rather than allocating a public long code mask to each subscriber (user).
It is also efficient to assign one physical channel to each service by taking the broadcast/multicast service as a reference, so that the assigned physical channel can be shared by various users. The shared physical channel for providing a broadcast/multicast service may be a forward fundamental channel (F-FCH) or a forward supplemental channel (F-SCH). Hence, the F-FCH channel is a forward broadcast fundamental channel (F-BFCH), and the F-SCH channel is a forward broadcast supplemental channel (F-BSCH). Regardless of the physical channel shared, however, a user group having the same Walsh code and public long code mask for a given service shares one channel that is assigned to one broadcast/multicast service, which defines a specific identifier (BCMC_FLOW_ID) for the provided service, so that one channel and one PLCM are assigned to the identifier. That is, each service has it own service identifier, which differs for the Walsh code and PLCM used for the corresponding channel, and the service identifier is generated by a base station and is transmitted to a mobile station.
Meanwhile, the PLCM used for F-BFCH and F-BSCH channels must be newly generated (assigned), to be distinguishable from a PLCM used for each user's previous forward or reverse fundamental channel and forward or reverse supplemental channel. The newly assigned PLCM cannot overlap (coincide with) a PLCM currently used by a base station controller. Avoiding this necessitates a transfer of the PLCM from a base station or anchor base station to the base station controller, i.e., a higher layer, resulting in an undesirable delay and complicating the related network functions.